These studies are designed to: (1) evaluate the influence of in utero exposure to environmental toxicants (for example, diethylstilbestrol) on fine structure of the male and female reproductive tracts; (2) study the influence of environmental chemicals on cell differentation and cell surface ultrastructural features; (3) develop and utilize models which will determine the cell surface features associated with preneoplastic and neoplastic transformation by scanning and transmission electron microscopy and correlate histology, (4) employ histochemistry to identify and localize morphological markers to assess the cellular or subcellular responsiveness to foreign agents, and (5) determine with autoradiography, the cellular and subcellular localization of steroid hormones in normal or abnormal reproductive tract tissues.